1. Field of the Invention
Embodiments of the invention relate to an apparatus and method used for the delivery of chemical precursors. More particularly, the invention relates to an ampoule configured with a valve manifold that includes a bypass line and a bypass valve.
2. Description of the Related Art
Chemical vapor deposition (CVD) and atomic layer deposition (ALD) are known techniques for forming a material on a substrate by the reaction of vapor phase chemicals near the surface of a substrate. In general, CVD and ALD techniques involve the delivery of gaseous reactants to the substrate surface where a chemical reaction takes place under temperature and pressure conditions favorable to the thermodynamics of the reaction. The type and composition of the layers that may be formed using a CVD process or an ALD process are limited by the ability to deliver a chemical reactant or precursor to the substrate surface. Various liquid precursors have been successfully used during CVD and ALD applications by delivering the liquid precursors within a carrier gas.
A carrier gas is in some cases passed through a heated container, or ampoule, which contains a volatile liquid precursor under conditions conducive to vaporize the precursor. In other cases, a carrier gas is passed through a heated container containing a solid precursor under conditions conducive to sublimation of the solid precursor. Some gases that may be produced through a sublimation process include xenon difluoride, nickel carbonyl, tungsten hexa-carbonyl, and pentakis dimethylamino tantalum (PDMAT) among others. In either case, the carrier gas combines with the vaporized precursor and both are drawn from the container via dedicated conduits or gas lines to a reaction chamber. Because the chemical precursors for CVD and ALD applications are typically highly toxic and because the heated container and chemical delivery components proximate thereto are generally at an elevated temperature, precursor-containing ampoules are typically located inside a protective housing, such as a gas cabinet or gas panel.
A typical gas panel for CVD or ALD applications contains various valves, regulators, and flow controllers in addition to one or more precursor-containing ampoules. For safety reasons, gas panels are also generally equipped with exhaust ventilation and are locked and alarmed to prevent possible exposure of personnel to the toxic precursors and heated components located therein. Because the removal and installation of precursor-containing ampoules requires entry into a gas cabinet by maintenance personnel, it is important to minimize the possibility of leakage from depleted ampoules when they are being removed and from fully charged ampoules when they are being installed.
A typical ampoule replacement procedure includes a number of steps including isolation, initial pump-purge, removal/replacement, leak check, final pump-purge, and connection.
In the isolation step, the spent precursor ampoule is fluidly isolated from the processing system, typically via manual shut-off valves located on the inlet and outlet plumbing of the ampoule. This typically requires entry into the gas cabinet by maintenance personnel despite proximity to gas panel components at elevated temperatures and the presence of unpurged gas lines containing highly toxic chemicals.
An initial pump-purge is then performed on any gas lines or valves that have been exposed to toxic agents and which will also be exposed to atmosphere during the ampoule change-out. The pump-purge may include pumping down the appropriate conduits, valves, and other fittings one or more times with a rough, medium, or high vacuum source, depending on the particular precursor used. Between pump-downs, the lines and valves may be purged with a gas, such as an inert gas. In some cases a liquid purge of conduits and valves may be performed to more efficiently remove unwanted and toxic residues present therein, particularly solid residues or residues with a very low vapor pressure. The removal of unwanted chemical residues from a conduit or valve via pump/purging is more effective when the gas or liquid used for purging can be actively passed through the conduit or valve. This is not possible wherever a “dead leg” is present, i.e., a section of pipe or conduit that does not form part of a constant circulation system. Instead, unwanted residues are removed from a dead leg by alternately pumping the dead leg down to vacuum and back-filling it with purge fluid, which is known in the art to be less effective than the active passage of purge fluid through a conduit or fitting. This is especially true for dead legs that are relatively long and/or contain elbows or other non-linear fittings.
After the pump-purge step has been completed with the requisite number of pump-purge cycles on the desired conduits, the removal/replacement of the ampoule may be performed. In this step, the ampoule is removed from the gas cabinet and a fully charged replacement is installed. The ampoule is typically separated from the gas cabinet by means of quick disconnect type fittings or re-sealable vacuum-tight fittings, such as VCR fittings. In some cases, the fluid delivery system that is exposed to atmosphere as a result of the ampoule replacement is slightly pressurized during the removal/replacement step with an inert gas. This slight pressurization minimizes entry into the fluid delivery system of unwanted contaminants, such as oxygen and/or moisture. The replacement ampoule is then connected to the fluid delivery system via the appropriate fittings in the gas cabinet.
Because CVD and ALD precursors are typically highly reactive and in some cases corrosive, it is known in the art that ampoule shut-off valves may not always be completely leak-tight-particularly after removal of a depleted ampoule from a gas cabinet. This is due to the prolonged exposure of the shut-off valves' sealing surfaces to the precursor chemical flowing therethrough during the lifetime of the ampoule. Any leakage of the ampoule shut-off valve is a serious issue for two reasons: the potential for contaminants to enter the ampoule and, more importantly, the potential for a dangerous precursor chemical to leak out of the ampoule and expose personnel to toxic chemicals.
After the replacement ampoule is installed, a helium leak check is typically performed on any fluid delivery connection points or other seals that were broken during ampoule removal/replacement. This generally involves pumping down the connection points to be tested to a relatively high level of vacuum.
When all connections have passed leak checking, a final pump-purge of the fluid delivery system associated with the ampoule replacement is performed. The final pump-purge is intended to maintain the ultra-high purity of chemicals delivered to a processing chamber after exposure of the fluid delivery system to airborne contaminants, such as moisture and oxygen. As described above for the initial pump-purge, the final pump-purge step generally includes alternately pumping down and fluidly purging conduits and other fittings that may have been exposed to atmospheric contaminants. While a final pump-purge step ensures a cleaner fluid delivery system for subsequent CVD or ALD processing, it may also precipitate leakage into or out of the newly charged ampoule due to the additional stresses placed on the ampoule shut-off valve resulting from alternately pressurizing and evacuating a conduit fluidly coupled thereto.
Finally, after the above steps have been completed, the new ampoule is fluidly connected to the fluid delivery system that terminates in the gas cabinet by opening the manual shut-off valves located on the inlet and outlet plumbing of the ampoule. As with the isolation step, this typically requires entry into the gas cabinet by maintenance personnel.
FIG. 1 is a simplified schematic of a conventional process gas delivery system. Fluid delivery system 202 is suitable for producing a process gas containing a chemical precursor and generally includes process chamber 206 and a carrier gas source 205 coupled to gas panel 204, the components of the latter being controlled by a controller 250. Gas panel 204 generally controls the rate and pressure at which various process and carrier gases are delivered to process chamber 206. Process chamber 206 may be a chamber to conduct vapor deposition processes or thermal processes containing a vaporized chemical precursor in liquid, gaseous or plasma state. Process chamber 206 is generally a chemical vapor deposition (CVD) chamber, an atomic layer deposition (ALD) chamber, or a derivative thereof. Examples of process chamber 206 include PRODUCER® CVD chambers and DzX® CVD chambers available from Applied Materials, Inc., located in Santa Clara, Calif., or an ALD chamber, such as that described in commonly assigned U.S. Pat. No. 6,916,398, filed Dec. 21, 2001.
In the configuration illustrated in FIG. 2, controller 250 includes central processing unit (CPU) 252, memory 254 and support circuits 256. Central processing unit 252 may be one of any form of computer processor that can be used in an industrial setting for controlling various chambers and subprocessors. Memory 254 is coupled to CPU 252 and may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), flash memory, compact disc, floppy disk, hard disk or any other form of local or remote digital storage. Support circuits 256 are coupled to CPU 252 for supporting CPU 252 in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry, subsystems and the like.
Fluid delivery circuit 236 is generally intended to fluidly couple carrier gas source 205, ampoule 200, and process chamber 206 as necessary for operation of process chamber 206. Carrier gas source 205 may be a local vessel, remote vessel or a centralized facility source that supplies the carrier gas throughout the facility (e.g., in-house gas supply). Carrier gas source 205 typically supplies a carrier gas such as nitrogen, hydrogen, argon, helium or combinations thereof. Additional purge fluid sources (not shown) may also be fluidly coupled to fluid delivery circuit 236 when the use of specialized purge fluids, such as a purge liquid, is required. Fluid delivery circuit 236 typically includes a flow controller 220 disposed between carrier gas source 205 and junction 230 and is adapted to modulate the flow rate of carrier gas or other fluids through fluid delivery circuit 236. Flow controller 220 may be a proportional valve, a modulating valve, a needle valve, a regulator, a mass flow controller (MFC) or the like. Junction 230 separates fluid delivery circuit 236 into gas generation line 238 and bypass line 240. Junction 232 rejoins gas generation line 238 and bypass line 240 before connecting to process chamber 206.
Gas generation line 238 includes ampoule inlet leg 238a, ampoule outlet leg 238b, valves 208, 210, 212, sensors 226, 228, disconnect fittings 262, 263, and heater 222. Ampoule inlet leg 238a fluidly couples the inlet of ampoule 200 to carrier gas source 205 and to bypass line 240. Ampoule outlet leg 238b fluidly couples the outlet of ampoule assembly 200 to process chamber 206 and to bypass line 240. Valves 208, 210 and 212 are typically remotely controllable shut-off valves that serve to divert the flow of fluids within fluid delivery circuit 236 and/or are used to selectively isolate the various components within fluid delivery circuit 236 to facilitate removal, replacement and/or service of an isolated component, including sensors 226, 228, heater 222, and ampoule assembly 200. Valves 208, 210, 212, as well as valves 214, 216, 218 (described below in conjunction with bypass line 240) are generally pneumatically or electronically controlled and the internal wetted surfaces thereof are fabricated from materials compatible with the process and other fluids handled by fluid delivery circuit 236. Typically, valves 208, 210, 212, 214, 216 and 218 are actuated in response to a signal from a controller 250 to coordinate the delivery of gases through fluid delivery circuit 236. Sensors 226, 228 are generally adapted to detect the temperature of a process, carrier, and/or purge fluid flowing through gas generation line 238, such as a thermocouple disposed against a conduit of gas generation line 238.
Bypass line 240 generally includes valves 214, 216 and heater 224 and serves to fluidly couple process chamber 206 and carrier gas source 205 without the use of gas generation line 238 or ampoule assembly 200. Valve 218 is generally coupled between junction 232 and process chamber 206 and may be used to isolate process chamber 206 from fluid delivery circuit 236. Heaters 222, 224 are resistive heating elements or other heat sources adapted to heat a flow of fluid, such as a carrier gas, flowing through gas generation line 238 and bypass line 240, respectively.
Ampoule assembly 200 generally contains an ampoule, or body 270, an inlet line 264, an outlet line 265, disconnect fittings 262b, 263b, and manual shut-off valves, manual valves 260, 261, disposed in inlet line 264, 265, respectively. Dead leg conduit segment 271b is disposed in inlet line 264 between manual valve 260 and disconnect fitting 262 and dead leg conduit segment 272b is disposed in outlet line 265 between manual valve 261 and disconnect fitting 263. Ampoule assembly 200 may also be referred to as a bubbler, a canister, and other terms known in the art to describe containers designed and used to store, transport and distribute chemical precursors. Inlet line 264 is coupled to ampoule inlet leg 238a at disconnect fitting 262 and outlet line 265 is coupled to ampoule outlet leg 238b at disconnect fitting 263. Disconnect fitting 262, 263 are typically adapted to facilitate removal and replacement of ampoule assembly 200 in gas panel 204 while leaving all other components of gas panel 204 in place, such as gas generation line 238 and its constituent parts. To this end, disconnect fittings 262, 263 typically include mating disconnect fittings 262a, 262b and 263a, 263b respectively, wherein disconnect fittings 262b, 263b are inherent to ampoule assembly 200 and corresponding disconnect fittings 262a, 263a are contained in fluid delivery circuit 236. Depending on the application, disconnect fittings 262a, 262b and 263a, 263b may be quick disconnect type fittings, re-sealable vacuum-tight fittings, such as VCR fittings, or other suitable disconnect fittings.
Ampoule assembly 200 may have a variety of sizes and geometries. Ampoule assembly 200 may have a volume capacitance of a chemical precursor within a range from about 0.5 L to about 10 L and more typically from about 1.2 L to about 4 L. In one example, ampoule assembly 200 has a volume capacitance of a chemical precursor of about 2.5 L. Chemical precursors that may be within ampoule assembly 200 include liquid, solid and gaseous precursors, preferably in liquid or fluid-like states at predetermined temperatures and/or pressures. For example, a chemical precursor may exist in the solid state at room temperature, but melts to the liquid state upon being heated to a predetermined temperature within the ampoule. In another example, the majority of a chemical precursor may remain in the solid state in the ampoule, but is heated to an elevated temperature during processing such that a small amount of the solid precursor sublimates directly into vapor. In another example, a chemical precursor may exist in the gaseous state at ambient pressure, but condenses to the liquid state upon being pressurized to a predetermined pressure within the ampoule. Chemical precursors may include alane complexes, such as 1-methylpyrolidrazine:alane (MPA, MeC4H3N:AlH3), pyridine:alane (C4H4N:AlH3), alkylamine alane complexes (e.g., trimethylamine:alane (Me3N:AlH3), triethylamine:alane (Et3N:AlH3), dimethylethylamine:alane (Me2EtN:AlH3)), trimethylaluminum (TMA, Me3Al), triethylaluminum (TEA, Et3Al), tributylaluminum (Bu3Al), dimethylaluminum chloride (Me2AlCl), diethylaluminum chloride (Et2AlCl), dibutylaluminum hydride (Bu2AlH), dibutylaluminum chloride (Bu2AlCl), water, hydrogen peroxide (H2O2), hydrazine (N2H4), titanium tetrachloride (TiCl4), tetrakis(dimethylamino)titanium (TDMAT, (Me2N)4Ti)), tetrakis(diethylamino)titanium (TEMAT, (Et2N)4Ti)), bis(ethylcyclopentadienyl)ruthenium ((EtCp)2Ru), tetrakis(dimethylamino)hafnium (TDMAH, (Me2N)4Hf)), tetrakis(diethylamino)hafnium (TDEAH, (Et2N)4Hf)), tetrakis(methylethylamino)hafnium (TMEAH, (MeEtN)4Hf)), tertiaryamylimido-tris(dimethylamido)tantalum (TAlMATA, (tAmylN)Ta(NMe2)3, wherein tAmyl is the tertiaryamyl group (C5H11— or CH3CH2C(CH3)2—), derivatives thereof or combinations thereof.
During processing, a carrier gas flows from carrier gas source 205 through fluid delivery circuit 236 to ampoule assembly 200. The carrier gas may be heated by heater 222, ampoule assembly 200 itself may be heated to a desired temperature, or in some applications, both the carrier gas and ampoule assembly 200 may be heated. During processing, valves 214 and 216 are closed, directing all carrier gas flow to process chamber 206 via gas generation line 238 and ampoule assembly 200.
During an initial pump-purge procedure performed prior to removing and replacing ampoule assembly 200, manual valves 260, 261 are closed. This isolates body 270 from gas generation line 238. During a pump-down segment of a pump-purge procedure, carrier gas source 205 is also isolated from fluid delivery circuit 236 by a shut-off valve (not shown) located between carrier gas source 205 and fluid delivery circuit 236. The vacuum source for process chamber 206 is typically used to pump down fluid delivery circuit 236 and dead leg conduit segments 271b, 272b of ampoule assembly 200. Alternatively, a dedicated vacuum source may be used, such as a vacuum pump fluidly coupled to fluid delivery circuit 236. In either case, all components of fluid delivery circuit 236 that are not isolated from the vacuum source are pumped down to a desired vacuum level, e.g. rough, medium, or high vacuum, by opening the requisite valves in gas panel 204. For example, when the vacuum source of process chamber 206 is used for pumping down fluid delivery circuit 236, valve 218 is opened to fluidly couple process chamber 206 to fluid delivery circuit 236, valves 214 and 216 are opened so that bypass line 240 fluidly couples ampoule inlet leg 238a to vacuum, and valves 210 and 212 are opened to fluidly couple conduit segments 271, 272 and dead leg conduit segments 271b, 272b to vacuum. The desired level of vacuum targeted during the pump-down segment depends on each particular CVD or ALD application and is a function of factors such as the vapor pressure of precursors and other residues being removed, fluid delivery line length, etc. It is important to note that it is necessary for maintenance personnel to enter gas panel 204 despite the presence of unpurged fluid delivery lines in order to close manual valves 260, 261 of ampoule assembly 200.
For a purge segment of a pump-purge procedure, a purge fluid source, such as carrier gas source 205, is fluidly coupled to fluid delivery circuit 236 and the desired purge fluid is introduced therein. The desired purge fluid may be a gas, such as an inert gas or other carrier gas, or a liquid, including solvents such as tetrahydrofuran (THF) or triglyme. Composition of the purge fluid depends on the physical state and chemical make-up of the chemical residues to be purged, solid particles and low vapor pressure liquids sometimes requiring one or more liquid solvent purges. Further, the purge fluid may also be heated during the purge segment to aid in the removal of unwanted chemical residue, either prior to be introduced into fluid delivery circuit 236 or by heaters 222,224. The vacuum source, such as process chamber 206 in one example, may be isolated from fluid delivery circuit 236 during the purge segment or it may be fluidly coupled thereto in order to continuously remove purge fluid throughout the purge segment. It is important to note that active flow of purge fluid occurs principally along bypass line 240 during a purge procedure. The only active flow of purge fluid into ampoule inlet leg 238a and ampoule outlet leg 238b occurs when these two sections of fluid delivery circuit are back-filled with purge fluid at the beginning of a purge segment. Hence, ampoule inlet leg 238a and ampoule outlet leg 238b act as extensive dead legs of significant length and potentially include numerous flow-restricting elbows. Further, the regions of fluid delivery circuit 236 that will be exposed to atmosphere during ampoule replacement, i.e. conduit segments 271, 272, and dead leg conduit segments 271b, 272b, are most likely to be contaminated and are the most important to purge thoroughly in preparation thereof. However, conduit segments 271, 272, and dead leg conduit segments 271b, 272b are located at the distal ends of the above-described dead legs and are, therefore, the most difficult regions of fluid delivery circuit 236 to purge effectively.
During removal, valves 210 and 212 are closed to fluidly isolate conduit segments 271, 272 from fluid delivery circuit 236, and disconnect fittings 262, 263 are separated to allow removal of ampoule assembly 200, wherein mating disconnect fittings 262b, 263b inherent to ampoule assembly 200 and are removed therewith. As noted above, it is known in the art that ampoule shut-off valves, i.e. manual valves 260, 261, may not always be completely leak-tight after prolonged exposure to the precursor chemicals contained in ampoule assembly 200. Because a single point of isolation is used for ampoule assembly 200 at inlet line 264 and outlet line 265, i.e. manual valves 260, 261, respectively, there is the potential of leakage into or out of ampoule assembly 200 during the removal of a depleted ampoule from gas panel 204. A freshly-charged ampoule is reconnected to fluid delivery circuit 236 at disconnect fittings 262, 263.
After installation of a new ampoule assembly 200, any fluid delivery connection points or other seals that were broken during ampoule removal/replacement are leak-checked, in this example disconnect fittings 262, 263. Leak checking ensures that contaminants are not drawn into fluid delivery circuit 236 and that toxic chemical precursors do not leak out of ampoule assembly 200 during processing. If either of disconnect fittings 262, 263 are not vacuum-tight, only a single point of isolation is present between the chemical contents of ampoule assembly 200 and any contaminants that may have leaked into dead leg conduit segments 271b, 272b. 
Therefore, there is a need for an apparatus and process to purge gas lines as completely as possible, to perform pump-purge procedures with minimal entry into a gas cabinet, and to decrease the possibility of leakage into or out of precursor-containing ampoules before, during, and after removal and installation of such ampoules.